1. Field of the Invention
The invention is directed to methods of post conversion for display devices.
2. Description of Related Art
An improved electrophoretic display technology is described in U.S. Pat. Nos. 6,930,818, 6,933,098 and 6,672,921, all of which are incorporated herein by reference in their entirety. An electrophoretic display film prepared by this technology comprises closed cells formed from microcups of well-defined shape, size and aspect ratio, filled with charged pigment particles dispersed in a dielectric solvent or solvent mixture and sealed with a polymeric sealing layer.
Other types of display (e.g., liquid crystal display, electrodeposition display, electrochromic display or the like) may also be prepared by the microcup technology (see, for example, U.S. Pat. Nos. 6,795,138; 7,141,279; and 7,245,414; and US Patent Application Publication No. 2005-001288;, all of which are incorporated herein by reference in their entirety).
A microcup-based electromagnetophoretic display (EMPD) technology is disclosed in U.S. Pat. No. 6,927,892, the content of which is also incorporated herein by reference.
The display devices mentioned above may be manufactured by laminating one or both sides of a display film with electrode layer(s). In the case of a passive matrix display device, a display film may be sandwiched between two patterned electrode layers in line format. For a segment display device, a display film is sandwiched between one common electrode layer and a patterned electrode layer which may be a printed circuit board. For an active matrix display device, a display film is sandwiched between a common electrode layer and a thin film transistor (TFT) layer. There may also be display devices such as display devices driven by an in-plane mode or electromagnetophoretic displays in which a display film is sandwiched between a common electrode layer and a substrate layer.
The common electrode layer(s) in a segment or active matrix display device often need to be partially exposed in order to be connected to a driver circuitry. For a passive matrix display device, one of the line patterned electrode layer also needs to be partially removed for electrical connection. Previously, in assembling a display device, the exposure of electrode lines was accomplished by asymmetric lamination of the electrode layers to a display film. Asymmetric lamination is a batch-wise process. In other words, the display film is laminated piece by piece; thus the process has a very low throughput.
In U.S. Pat. No. 6,873,452, the content of which is incorporated herein by reference in its entirety, a post conversion process involving solvent stripping is described. In such a process, a solvent (e.g., acetone or methylethyl ketone) is used to remove a portion of the display film in order to expose electrode lines of the electrode layers laminated to the display film. Before stripping, however, the part of the display film not to be removed must first be edge sealed by covering it with a releasable protection film to protect it from the stripping solvent and the stripping step must also be carried out in a very gentle manner in order to protect both the electrode layers and the display film not to be removed. Such a process therefore is difficult to implement in large scale manufacturing.
Alternatively, dry brush may be used to remove part of the display film to expose the common electrode or electrode lines on an electrode layer. However, the debris of the removed film tends to be attached to the brush, thus significantly reducing the processing speed. The dry brush method may also generate cross-contamination.